The present inventors have developed and introduced a double-biprism electron interferometer (Japanese Patent Applications Nos. 2004-004156 and 2004-102530, and Non-Patent Documents 1 and 2). In the invention, two electron biprisms are arranged in order of the traveling direction of an electron beam on an optical axis in such a manner that the upper-stage biprism is located on an image plane of a specimen observed and that the lower-stage biprism is located in the shadow area of the upper-stage biprism and voltages applied to their respective filament electrodes of the electron biprisms are changed so that an overlap area (corresponding to an interference area width W) and an overlap angle (corresponding to an interference fringe spacing s) of two electron waves (e.g., an object wave and a reference wave) can be changed arbitrarily. The upper-stage electron biprism is located on the image plane of the specimen, making it possible to eliminate generation of Fresnel fringes superimposed on an interference area, such as a hologram, which cannot be eliminated, in principle, in an electron interferometer using one electron biprism (for instance, Patent Document 1).
In addition to this, the present inventors have proposed an invention in which an azimuth angle Φ is introduced between filament electrodes of two electron biprisms to control an azimuth θ of the interference fringes (Japanese Patent Application No. 2005-027274).
There is an interferometer using a charged particle beam such as an electron or ion or an optical interferometer using light beam. In the present invention, the interferometer using an electron beam will be mainly described.
Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2002-117800
Non-Patent Document 1: “Double-Biprism Electron Interferometory”, Ken Harada, Tetsuya Akashi, Yoshihiko Togawa, Tsuyoshi Matsuda and Akira Tonomura, Applied Physics Letter: Vol. 84, No. 17, (2004) pp. 3229-3231.
Non-Patent Document 2: “High-Resolution Observation by Double-Biprism Electron Holography”, Ken Harada, Tsuyoshi Matsuda, Tetsuya Akashi, Yoshihiko Togawa and Akira Tonomura, Journal of Applied Physics: Vol. 96, No. 9, (2004) pp. 6097-6102.